JP2001275150A - Wireless base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a wireless base station that is not susceptive to influence of a delay wave on a control signal in order to improve the error rate characteristics of a control channel. SOLUTION: Transmission/reception of a control channel are conducted for each sector, and all sectors under the control of a base station are sequentially switched to broadcast.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for space division multiple access (SDMA) in which a radio base station performs radio communication at the same frequency simultaneously with a plurality of mobile stations with different directivities.

[0002]

2. Description of the Related Art Space division multiple access (SDMA) refers to multiple access in which a radio base station forms different directivities for a plurality of mobile stations and simultaneously performs radio communication with a plurality of mobile stations on the same channel. (Multi-Beam Adaptive
Base-station Antennas for Cellular Land Mobile Ra
dio System: SCSwales, IEEE VTC, 1989).

[0003] This conventional example will be described with reference to FIGS. 4 and 5. FIG. 4 is a conceptual diagram showing a state in which one radio base station performs radio communication with two different mobile stations with different directivities. FIG. 5 is a conceptual diagram showing a state in which one wireless base station performs wireless communication with two different mobile stations using one omni-directional (omni-directional) antenna.

As shown in FIG. 4, a radio base station BS directs its main beams # 1 and # 2 to mobile stations MS1 and MS2 using antennas capable of forming two different directivities. , Wireless communication can be simultaneously performed with the mobile stations MS1 and MS2 using the same channel.

On the other hand, as shown in FIG.
When transmitting and receiving with omni-directionality, only one mobile station can perform wireless communication on the same channel. That is, the subscriber capacity that can be accommodated in one channel by SDMA can be increased.

However, when transmitting a control signal, such as an incoming call signal and a broadcast signal, which needs to transmit a radio signal to all mobile stations under the control of the radio base station, directivity is set in a specific direction by SDMA. It cannot be sent or received.

For example, an incoming call signal needs to be broadcasted because the radio base station does not know the position of the mobile station. Also, a position information signal for identifying the control zone, a transmission control channel information signal for notifying the mobile station of the number of the transmission control channel being used, and that there is no signal from the mobile station in the uplink transmission control channel and that the transmission is free. Since the broadcast signal such as the free line signal of the transmission control channel shown is a signal for all mobile stations, it needs to be transmitted to mobile stations in all directions.

Therefore, in the prior art, as shown in FIG. 5, control signals such as an incoming call signal and a notification signal are transmitted and received in omni-directionality. Note that the notification signal described above is a model case and may be different in other systems. On the other hand, the control channel associated with the communication channel and the communication channel for controlling the channel switching during communication is a channel intended for a specific mobile station, and can perform SDMA with directivity directed to the specific mobile station. .

[0009]

As described above, when the control signal is received in the omni-directional pattern by the conventional technique, all the delayed waves input from all directions are received, and the directivity is given to a specific mobile station. There is a problem that it is more susceptible to delayed waves as compared with the case of forming. In other words, the effect of the selective fading increases.

On the other hand, in the method of forming directivity in a specific mobile station, a desired wave arriving from the direction of the main beam is strongly received, and a delayed wave arriving from another direction is affected by the delayed wave. Hateful.

That is, in the prior art, a control signal such as an incoming call signal and an annunciation signal transmitted / received with omni-directionality has a delayed wave compared to a call signal transmitted / received with directivity formed at a specific mobile station. However, there is a disadvantage in that it is susceptible to the influence of selective fading.

The present invention has been made in view of such a background, and an object of the present invention is to provide a radio base station in which a control signal is hardly affected by a delayed wave. The present invention
An object of the present invention is to provide a radio base station capable of improving the error rate characteristics of a control channel.

[0013]

The most important feature of the present invention is that transmission and reception of a control channel are performed for each sector, and all sectors under the control of a base station are sequentially switched for broadcasting. It differs from the prior art in that it uses sector antenna switching instead of omni-directional to achieve control channel broadcasting.

According to the present invention, the number of delayed waves to be received can be reduced by using a sector antenna for transmission and reception of a control channel that needs to be broadcast, as compared with the case of using omni-directivity. The effect can be reduced, and the effect of improving the error rate characteristics of the control channel can be obtained.

That is, the present invention provides a means for performing wireless communication for an unspecified mobile station, a means for performing wireless communication for a specific mobile station, and the directivity of which can be set in a plurality of different directions. The means that includes an antenna and performs wireless communication for the specific mobile station is a wireless base station that includes means for setting the directivity of the antenna to the direction of the mobile station.

Here, a feature of the present invention is that a plurality of sector antennas are provided in which the entire circumferential direction (360 °) is divided into a plurality of angles, and the divided angles are respectively assigned to the plurality of sector antennas. The means for performing wireless communication for the mobile station is provided with means for sequentially and cyclically switching and selecting the plurality of sector antennas.

Alternatively, the means for performing wireless communication for the specific mobile station may commonly use the plurality of sector antennas used by the means for performing wireless communication for the unspecified mobile station.

[0018] With this, even in wireless communication for an unspecified mobile station, transmission and reception can be performed for each sector, so that the effects of delayed waves can be reduced and the error rate characteristics of the control channel can be improved. be able to. At this time, if it is assumed that the switching selection speed is higher than the propagation speed of the delay wave, the effect of reducing the influence of the delay wave is considered to be reduced, but the switching selection speed is increased as such. There is no necessity, and the propagation speed of the delay wave is set to be extremely low compared with the propagation speed of the delay wave, so that the effect of reducing the influence of the delay wave can be sufficiently obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a radio base station according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a wireless base station according to a first embodiment of the present invention. FIG. 3 is an overall configuration diagram of a wireless base station according to the second embodiment of the present invention.

The first embodiment of the present invention, as shown in FIG.
A transceiver TR having means for performing wireless communication by a control channel for an unspecified mobile station, and means for performing wireless communication by a speech channel and a control channel associated with the speech channel for a particular mobile station; The system control device CO includes an antenna A including a plurality of antenna elements A1 to Ak whose directivity can be set in a plurality of different directions, and the system control device CO performs wireless communication targeting a specific mobile station. In this case, the wireless base station includes a weight control unit WCO for setting the directivity of the antenna A in the direction of the mobile station.

The feature of the first embodiment of the present invention is that the entire circumferential direction (360 °) is divided into a plurality of angles, and the plurality of sector antennas 1 to k to which the divided angles are respectively assigned. Is provided, and the system control device CO
When performing wireless communication targeting unspecified mobile stations,
The plurality of sector antennas 1 to k are sequentially and cyclically switched and selected.

Further, in the second embodiment of the present invention, as shown in FIG. 3, a set of sector antennas 1 to k is provided, and the system controller CO performs radio communication for a specific mobile station. Selects a sector antenna i having directivity in the direction of the mobile station, and when performing wireless communication for an unspecified mobile station, sequentially switches and selects a plurality of sector antennas 1 to k.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a diagram for explaining the concept of a sector. As shown in FIG. 1, since it is necessary to form directivity for a specific mobile station by SDMA,
A plurality (k) of antenna elements A1 to Ak are required.
Complex amplitudes x1 to x which are outputs of antenna elements A1 to Ak
k is set to a complex weight w1 by a complex weight multiplier WMU.
Ｗwk, and the adder AD obtains the sum output y. Although the individual directivities of the antenna elements A1 to Ak are omni-directional, the directivity of the antenna A can be formed in a specific direction by changing the complex weights w1 to wk. The sum output y is input to a receiver via a switch in the transceiver TR and demodulated to obtain information.

Several algorithms are known as a directivity forming method when performing SDMA, but when classified based on prior knowledge about a desired wave, it is divided into two systems.
One is a method using a replica of a desired wave as prior knowledge, and is an algorithm called MMSE (RLS, LMS) that forms directivity by the least square method using the replica as a reference signal. The other is a method using the arrival direction (DOA) of a desired wave as prior knowledge.
An algorithm called CMP is known.

In addition, C is used to form directivity blindly without prior knowledge using the property of constant envelope of signals.
There is also an algorithm called MA. In these methods, the main beam is directed to a desired wave, and null is directed to an interference wave. In addition, fixed beamforming that suppresses the interference wave by pointing the main beam to the desired wave and forming a low-gain directivity pattern in directions other than the desired wave, instead of pointing the null to the interference wave Method is also SD
Can be used in MA. The wireless base station is provided with a weight control unit WCO for controlling a complex weight.

In the above description, the signal flow is for reception, but for transmission, the signal flow may be reversed by using the receiver as a transmitter and the adder as a splitter. The above apparatus is an apparatus for performing SDMA, and signals transmitted and received by this apparatus are speech signals for directing directivity to a specific mobile station. When using SDMA that directs the directivity to a specific mobile station, the directivity can be narrowed, so that the transmission of a speech signal is less susceptible to delay waves.

However, if a control channel that needs to be broadcast, such as an incoming call signal and a broadcast signal, is transmitted in omni-directivity as in the prior art, a delayed wave arriving from any angle will be received. It has the disadvantage of being strongly affected by delayed waves.

In the present invention, in order to avoid this problem, when transmitting and receiving control channels, separately provided sector antennas 1 to k are used. Because the sector antenna 1
This is because k can narrow the directivity as compared with the case of transmitting and receiving with omni directivity, so that the number of delayed waves can be reduced, and therefore, it is resistant to delayed waves.

As a result, it is possible to solve the drawbacks of the prior art such as the deterioration and disconnection of the transmission quality of the control channel, which has been a problem when implementing SDMA in mobile communication. Note that a sector is an area obtained by dividing a cell into several parts as shown in FIG. Sector antenna 1
No. 3 forms directivity so as to cover only sectors # 1 to # 3. Sector antenna 1 that switches sequentially
By transmitting and receiving a control signal using k, transmission and reception can be performed with all mobile stations existing in the cell. That is, broadcasting can be performed. As shown in FIG. 1, the base station is provided with a sector selector switch SE for switching sector antennas. The sector antennas 1 to k are switched by sequentially switching the sector selector switch SE.

The sector selector switch SE is connected to the transceiver TR, and the transceiver TR is shared between transmission and reception of control signals and transmission and reception of speech signals.
The system control device CO controls each unit in a comprehensive manner.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. In the second embodiment, instead of separately providing the antenna A of the first embodiment, the sector antennas 1 to k are used for each antenna element that performs SDMA. When performing SDMA, complex weights w1 to
By controlling wk to form directivity, it acts as an adaptive array of beam spaces.

On the other hand, when used as a sector antenna, only the weight of the target antenna element is set to 1, and
Other weights are set to 0 for transmission / reception. Since each antenna element is a sector antenna, directivity can be formed only in the sector. The antenna can be switched by changing the antenna element whose weight is 1.

[0033]

As described above, according to the present invention,
It is possible to reduce the influence of a delayed wave generated when transmitting and receiving a control signal. Thereby, the error rate characteristics of the control channel can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a wireless base station according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining sectors.

FIG. 3 is an overall configuration diagram of a wireless base station according to a second embodiment of the present invention.

FIG. 4 is a conceptual diagram showing a state where one wireless base station performs wireless communication with two different mobile stations with different directivities.

FIG. 5 is a conceptual diagram showing a state where one wireless base station performs wireless communication with two different mobile stations using one omni-directional (omni-directional) antenna.

[Explanation of symbols]

 1 to k sector antenna A antenna A1 to Ak antenna element AD adder, splitter BS radio base station CO system controller MS1, MS2 mobile station SE sector selector switch TR transceiver WCO weight controller WMU complex weight multiplier w1 wk complex weight x1-xk complex amplitude

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01Q 21/28 H01Q 25/00 25/00 H04J 15/00 H04B 7/26 H04B 7/26 105D H04J 15 / 00 B (72) Inventor Shuji Kubota 2-3-1 Otemachi, Chiyoda-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 5J021 AA05 AA08 AA10 AA12 CA06 DB02 DB03 DB04 EA04 FA05 FA14 FA15 FA16 FA17 FA20 FA24 FA26 FA29 FA31 FA32 GA02 GA08 HA03 HA05 HA10 JA03 5K022 FF04 5K067 AA02 CC01 EE02 EE10 EE22 EE46 HH21 KK02

Claims (2)

[Claims] 1. A wireless communication system comprising: means for performing wireless communication for an unspecified mobile station; means for performing wireless communication for a specific mobile station; and an antenna whose directivity can be set in a plurality of different directions. The means for performing wireless communication for the specific mobile station,
In a radio base station comprising means for setting the directivity of the antenna in the direction of the mobile station, a plurality of sectors to which the entire circumferential direction (360 °) is divided into a plurality of angles and the divided angles are respectively assigned. A wireless base station provided with an antenna, wherein the means for performing wireless communication with the unspecified mobile station includes means for sequentially and cyclically switching and selecting the plurality of sector antennas. 2. A means for performing wireless communication for an unspecified mobile station, a means for performing wireless communication for a specific mobile station, and dividing the entire circumferential direction (360 °) into a plurality of angles. A plurality of sector antennas each assigned a given angle, means for performing wireless communication for the specific mobile station,
In a radio base station comprising means for selecting the sector antenna having directivity in the direction of the mobile station, the means for performing wireless communication for the unspecified mobile station includes: A radio base station characterized by comprising means for switching and selecting.